yolco
Member level 2

The next circuit was thought to detect noise by a MCU. It is a preamplification stage for an electret microphone.

R22 & R23 help to provide Bias current to MIC.
'Mute point' is set at 1.65V with R23 & R24.
But I have some doubts about how decide the right configuration for amplifier.
The commercial solution I'm thinking to work with is the MAX4467.
Kind Regards.

R22 & R23 help to provide Bias current to MIC.
'Mute point' is set at 1.65V with R23 & R24.
But I have some doubts about how decide the right configuration for amplifier.
- GAIN:
- Voltage supply is 3V3 (VDD).
- Gain has to be calculated to get the highest output voltage without clipping [Av=-R32/R31]. So, now it has a gain of -100.
- From MIC supplier, I now the max output voltage from MIC is 8mV.
- Which would the suitable gain for this application? How can I calculate it for getting a max output voltage of 3V3?
- FILTERS:
- As the desired range is [100Hz - 20 kHz], C32 value should be changed.
- Will 7pF capacitor enough for a low-pass filter (f3dB=22kHz)?
The commercial solution I'm thinking to work with is the MAX4467.
Kind Regards.